The Chinese rice grasshopper, Oxya chinensis Thunberg (Orthoptera: Catantopidae), is an important pest in rice paddy fields, and is widely distributed throughout China except for the cold and dry northwestern provinces and autonomous regions of Qinghai, Tibet, Xinjiang, and Inner Mongolia. It is known to be univoltine in northern China and bivoltine in southern China, and it shows a complex pattern of latitudinal variation in diapause induction. Eggs of both the northern and southern populations of O. chinensis enter diapause and overwinter. The incidence of diapause is genetically determined in the northern populations and regulated by maternal photoperiod and incubation temperature in the southern populations. In populations at intermediate latitudes, diapause is only affected by the incubation temperature of eggs. To understand the life cycle and seasonally adaptive traits of O. chinensis in a Changsha population (28.2°N, 113.0°E), we investigated the number of generations per year, seasonal variation in egg hatching and diapause rate, and survival of overwintering eggs in the field and laboratory. The results indicated that the Changsha population of O. chinensis showed a uni-bivoltine mixed life cycle with non-diapause and diapause eggs in the first generation. Non-diapause eggs subsequently hatched and completed two generations per year. Diapause eggs overwintered and completed only one generation per year. Adults of the first generation appeared from early June to early August and oviposited from late June to mid-August. Nymphs of the second generation started appearing in early July and emerged as adults from September to October, with most individuals finishing oviposition by late November. In the field, eggpods obtained from June to August (the first generation) or from October to November (the second generation) were all enter diapause partially in this Changsha population of O. chinensis. The diapause rate was about 30% and it did not significantly differ among different months. However, the diapause rate of eggs exposed to field conditions significantly decreased after December, to only 6.6% at most, indicating that the eggs had terminated their diapause spontaneously because of the low temperatures before the end of winter. Thus, both non\\diapause and diapause O. chinensis eggs overwintered in a non-diapause state through the subsequent cold season in Changsha. Freezing rain swept across large areas south of Yangtze River from the end of 2007 to early 2008 and the winter was unusually cold at our experimental site. However, the survival rate of overwintered eggs was more than 98%, as assessed in the following spring. These results reveal that non-diapause eggs are able to safely overwinter, and diapause does not seem to be an adaptation to improve the cold tolerance of eggs in the Changsha population of O. chinensis. Additionally, this paper also discusses the evolutionary significance of egg diapause in Changsha population of O. chinensis.